Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface, showing the first image in a sequence, showing our new design;

FIG. 2 is a front view showing the second image thereof;

FIG. 3 is a front view showing the third image thereof;

FIG. 4 is a front view showing the fourth image thereof;

FIG. 5 is a front view showing the fifth image thereof;

FIG. 6 is a front view showing the sixth image thereof;

FIG. 7 is a front view showing the seventh image thereof;

FIG. 8 is a front view showing the eighth image thereof;

FIG. 9 is a front view showing the ninth image thereof; and,

FIG. 10 is a front view showing the tenth image thereof.

The outermost broken lines illustrating portions of a display screen or portion thereof form no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-10. The process or period in which one image transitions to another image forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 